The just-ended 10th National Games provided an opportunity for China to showcase its sporting credentials ahead of hosting the 2008 Olympics. Instead, the event has highlighted the unacceptable face of mainland sport.

Who can forget the scene of judo player Sun Fuming falling on the floor and conceding defeat after her opponent, a fellow competitor from Liaoning province lent to the People's Liberation Army team, barely touched her on the shoulder? When a rematch was held, Sun again lost in incredulous circumstances, apparently to honour a deal between the PLA and the provincial team.

The affair, captured on video, sparked national outrage. Hong Kong badminton player Wang Chen did not have the benefit of the cameras. She lost in the semi-finals of the women's singles and complained about unfair calls by the umpire. But the match was the only semi-final not telecast, depriving her of any video evidence with which to launch an appeal. Wang protested by abandoning her women's singles bronze medal match.

Sadly, these were not isolated incidents. At some other matches across a wide range of sports, the outcomes were so preposterous that they cannot be explained just by bad umpiring. Star players who had excelled in international competitions complained that they lost because the results had been fixed. There were also widespread allegations of players using illegal drugs to boost their performances.

With three years to go before China hosts the Olympics, the National Games should have highlighted the strength of Chinese athletes and the organisational prowess of the authorities. But the spate of scandals about match-fixing and doping have left local and foreign observers aghast at the poor quality of Chinese referees and corrupt state of Chinese sport.

It is now imperative for Beijing to investigate all the allegations and introduce measures to restore and safeguard the integrity of its sporting regime. If it fails to clean up its own house, it will not be able to assure international athletes that their performance at the Olympics will be properly assessed and honoured.

The slogan 'friendship first, competition second' used to adorn every sporting venue on the mainland. The saying underlined Beijing's use of sport as a diplomatic tool to reach out to the outside world. Today, the slogan has taken a back seat, but sport remains a means of projecting China's national image.

Sport cannot be a tool for promoting China if it is plagued by under-the-table deals. It is time Beijing set sport free of its political mission. There is no reason to believe Chinese athletes, liberated from the shackles of officialdom, will cease to excel. And corruption should become less of a problem. The unhappy experience of the National Games could help ensure that the Beijing Olympics is a big success. But only if lessons are learned and action taken to clean up mainland sport.